Chemical Vapor Deposition (CVD) from metal-organic compounds allows formation of thin films of a variety of materials by decomposition of molecular, metal-organic species. The primary advantages of CVD over other methods, such as physical vapor deposition (PVD), are that conformal coverage of complex structures is enabled and selective deposition is possible. These two aspects are particularly important in electronics applications in which surfaces with complex microelectronic topographies must be coated. An example is the formation of metal interconnect structures, which consist of a three dimensional network of metal features.
The metals of primary interest for interconnect structures are W, A1 and Cu. Each has distinct advantages and disadvantages. Selective and blanket deposition of high purity tungsten using WF.sub.6 has been demonstrated, and CVD of A1 has been studied extensively. However, the resistivities of tungsten and aluminum are too high for many proposed metallization schemes. Thus, CVD of Cu is the subject of much current interest due to its low resistivity (1.67 .mu.ohmcm at 20.degree. C.) relative to other metals (W, 5.65 .mu.ohmcm; Al, 2.65 .mu.ohmcm) and its good resistance to electromigration relative to aluminum.
A series of precursor metal-organic copper(I) compounds, (.beta.-diketonate)CuL.sub.n, where L=Lewis base, n=1 or 2, have recently been identified that are suitable for the chemical vapor deposition of copper and are capable of systematic substitution of .beta.-diketonate and L where L=PMe.sub.3, 1,5-Cyclooctadiene (COD), vinyltrimethylsilane (VTMS) and 2-butyne to tailor volatility and reactivity. These compounds are discussed in the following publications: Shin. H. K.; Chi, K. M.; Farkas, J.; Hampden-Smith, M. J.; Kodas, T. T.; Duesler, E. N. Inorg. Chem., 1992, 31, 424; Shin, H. K.; Chi, K. M.; Hampden-Smith, M. J.; Kodas, T. T.; Paffett, M. F.; Farr, J. D. Angew. Chem. Advanced Materials, 1991, 3, 246; Jain, A.; Chi, K. M.; Hampden-Smith, M. J.; Kodas, T. T.; Paffett, M. F.; Farr, J. D. Chem. Mat. 1991, 3, 995; Chi, K. M.; Shin, H. K.; Hampden-Smith, M. J.; Kodas, T. T.; Duesler, E. N. Polyhedron, 1991, 10, 2293; Chi, K. M. Shin, H. K.; Hampden-Smith, M. J.; Kodas, T. T.; Duesler, E. N. Inorg. Chem., 1991, 30, 4293; Jain. A.; Chi, K. M.; Hampden-Smith, M. J.; Kodas, T. T.; Paffett, M. F.; Farr, J. D., J. Mater. Res., 1992, 7, 261.
The precursors discussed in the foregoing publications can deposit copper via thermally induced disproportionation reactions such as: EQU 2(.beta.-diketonate)Cu.sup.I L.sub.n .fwdarw.Cu.sup.0 +Cu.sup.II (.beta.-diketonate).sub.2 +2nL (1)
Ligand decomposition is not required, since thermally-induced disproportionation occurs at temperatures at which the volatile Lewis base and the copper(II) product are transported out of the reactor intact.
The deposition characteristics of these compounds on unmodified SiO.sub.2 /metal substrates are described in Table 1 where CVD experiments were carried out under the conditions described in Section A below:
TABLE 1 ______________________________________ Cu deposition on unmodified SiO.sub.2 surfaces Deposition Temperature range Precursor Characteristics of Deposition ______________________________________ (hfac)Cu(PMe.sub.3) Pt, W, Cu vs. 150.degree. C.-300.degree. C. unmodified SiO.sub.2 (tfac)Cu(PMe.sub.3) Pt, W, Cu vs. 100.degree. C.-150.degree. C. unmodified SiO.sub.2 (acac)Cu(PMe.sub.3) Pt, W, Cu vs. &lt;80.degree. C. unmodified SiO.sub.2 (hfac)Cu(1,5-COD) none for Pt, W, Cu vs. 120.degree. C.-250.degree. C. unmodified SiO.sub.2 (hfac)Cu(VTMS) none for W vs. 120.degree. C.-250.degree. C. unmodified SiO.sub.2 (hfac)Cu(BTMS) none for Pt, W, Cu vs. 120.degree. C.-250.degree. C. unmodified SiO.sub.2 (hfac)Cu(2-butyne) none for Pt, W, Cu vs. 120.degree. C.-250.degree. C. unmodified SiO.sub.2 (hfac)Cu(2-pentyne) none for Pt, W, Cu vs. 120.degree. C.-250.degree. C. unmodified SiO.sub.2 ______________________________________